In recent years, a TFET (Tunnel Field-Effect Transistor) using a quantum mechanical effect of electrons has been developed. In the TFET, BTBT (Band To Band Tunneling) is caused between a source and a channel by applying a voltage to a gate electrode. This brings the TFET into an on-state.
In the TFET, it is considered to set the impurity concentration profile of a source layer to be abrupt in order to obtain steep sub-threshold characteristics. In order to set the impurity concentration profile to be abrupt, ion implantation for forming the source layer needs to be performed shallowly and in a high dose amount. It is known that the impurity concentration profile of a diffusion layer formed shallow and in a high concentration generally varies greatly in a wafer plane due to subsequent heat treatment or the like. Variations in the impurity concentration profile lead to variations in electrical characteristics (a threshold voltage, for example) of the TFET. For example, when variations in the threshold voltage are large, a power supply voltage for a circuit cannot be lowered in consideration of inclusion of a TFET with a high threshold voltage in the circuit. Therefore, a low-power circuit to which the power supply voltage is kept low is difficult to configure with the conventional TFETs.